Apparatus and Method for Visual Stimulation Indication

ABSTRACT

Methods and devices for verifying that proper visual stimulation is applied to the visual prostheses are described. In one of the methods, a retinal stimulation system implanted on a subject is simulated externally. An external testing device is also discussed.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of application Ser. No. 11/880,010,entitled “Apparatus and Method for Visual Stimulation Indication”, filedJul. 19, 2007, which claims the benefit of U.S. provisional PatentApplication Ser. No. 60/832,231, filed Jul. 20, 2006 for “Apparatus andMethod for Visual Stimulation Indication”, the disclosure of which isincorporated herein by reference.

FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

The present invention was made with support from the United StatesGovernment under Grant number R24EY12893-01, awarded by the NationalInstitutes of Health. The United States Government has certain rights inthe invention.

FIELD

The present disclosure relates to visual prostheses. More particularly,the present disclosure relates to verifying that proper visualstimulation is applied to the visual prostheses.

BACKGROUND

In 1755 LeRoy passed the discharge of a Leyden jar through the orbit ofa man who was blind from cataract and the patient saw “flames passingrapidly downwards.” Ever since, there has been a fascination withelectrically elicited visual perception. The general concept ofelectrical stimulation of retinal cells to produce these flashes oflight or phosphenes has been known for quite some time. Based on thesegeneral principles, some early attempts at devising a prosthesis foraiding the visually impaired have included attaching electrodes to thehead or eyelids of patients. While some of these early attempts met withsome limited success, these early prosthetic devices were large, bulkyand could not produce adequate simulated vision to truly aid thevisually impaired.

In the early 1930's, Foerster investigated the effect of electricallystimulating the exposed occipital pole of one cerebral hemisphere. Hefound that, when a point at the extreme occipital pole was stimulated,the patient perceived a small spot of light directly in front andmotionless (a phosphene). Subsequently, Brindley and Lewin (1968)thoroughly studied electrical stimulation of the human occipital(visual) cortex. By varying the stimulation parameters, theseinvestigators described in detail the location of the phosphenesproduced relative to the specific region of the occipital cortexstimulated. These experiments demonstrated: (1) the consistent shape andposition of phosphenes; (2) that increased stimulation pulse durationmade phosphenes brighter; and (3) that there was no detectableinteraction between neighboring electrodes which were as close as 2.4 mmapart.

As intraocular surgical techniques have advanced, it has become possibleto apply stimulation on small groups and even on individual retinalcells to generate focused phosphenes through devices implanted withinthe eye itself. This has sparked renewed interest in developing methodsand apparatuses to aid the visually impaired. Specifically, great efforthas been expended in the area of intraocular visual prosthesis devicesin an effort to restore vision in cases where blindness is caused byphotoreceptor degenerative retinal diseases such as retinitis pigmentosaand age related macular degeneration which affect millions of peopleworldwide.

Neural tissue can be artificially stimulated and activated by prostheticdevices that pass pulses of electrical current through electrodes onsuch a device. The passage of current causes changes in electricalpotentials across visual neuronal membranes, which can initiate visualneuron action potentials, which are the means of information transfer inthe nervous system.

Based on this mechanism, it is possible to input information into thenervous system by coding the information as a sequence of electricalpulses which are relayed to the nervous system via the prostheticdevice. In this way, it is possible to provide artificial sensationsincluding vision.

One typical application of neural tissue stimulation is in therehabilitation of the blind. Some forms of blindness involve selectiveloss of the light sensitive transducers of the retina. Other retinalneurons remain viable, however, and may be activated in the mannerdescribed above by placement of a prosthetic electrode device on theinner (toward the vitreous) retinal surface (epiretial). This placementmust be mechanically stable, minimize the distance between the deviceelectrodes and the visual neurons, and avoid undue compression of thevisual neurons.

In 1986, Bullara (U.S. Pat. No. 4,573,481) patented an electrodeassembly for surgical implantation on a nerve. The matrix was siliconewith embedded iridium electrodes. The assembly fit around a nerve tostimulate it.

Dawson and Radtke stimulated cat's retina by direct electricalstimulation of the retinal ganglion cell layer. These experimentersplaced nine and then fourteen electrodes upon the inner retinal layer(i.e., primarily the ganglion cell layer) of two cats. Their experimentssuggested that electrical stimulation of the retina with 30 to 100 uAcurrent resulted in visual cortical responses. These experiments werecarried out with needle-shaped electrodes that penetrated the surface ofthe retina (see also U.S. Pat. No. 4,628,933 to Michelson).

The Michelson '933 apparatus includes an array of photosensitive deviceson its surface that are connected to a plurality of electrodespositioned on the opposite surface of the device to stimulate theretina. These electrodes are disposed to form an array similar to a “bedof nails” having conductors which impinge directly on the retina tostimulate the retinal cells. U.S. Pat. No. 4,837,049 to Byers describesspike electrodes for neural stimulation. Each spike electrode piercesneural tissue for better electrical contact. U.S. Pat. No. 5,215,088 toNorman describes an array of spike electrodes for cortical stimulation.Each spike pierces cortical tissue for better electrical contact.

The art of implanting an intraocular prosthetic device to electricallystimulate the retina was advanced with the introduction of retinal tacksin retinal surgery. De Juan, et al. at Duke University Eye Centerinserted retinal tacks into retinas in an effort to reattach retinasthat had detached from the underlying choroid, which is the source ofblood supply for the outer retina and thus the photoreceptors. See,e.g., E. de Juan, et al., 99 μm. J. Opthalmol. 272 (1985). These retinaltacks have proved to be biocompatible and remain embedded in the retina,and choroid/sclera, effectively pinning the retina against the choroidand the posterior aspects of the globe. Retinal tacks are one way toattach a retinal array to the retina. U.S. Pat. No. 5,109,844 to de Juandescribes a flat electrode array placed against the retina for visualstimulation. U.S. Pat. No. 5,935,155 to Humayun describes a visualprosthesis for use with the flat retinal array described in de Juan.

In outer retinal degeneration, such as retinitis pigmentosa (RP), thephotoreceptors and their supporting retinal pigment epithelium areimpaired. In RP (incidence 1:4000) legal blindness is reached after 25years. In many RP patients over sixty years of age, elementary visionwith only gross movement or bright light perception remains, with littleor no appreciable peripheral vision. Eventually, even light perceptionmay recede. Currently, there is no treatment that stops or reverses theloss of photoreceptors in retinitis pigmentosa.

Traditionally, the approach to vision rehabilitation in subjects withretinitis pigmentosa has been to use the remaining vision with opticalaides. If no useful vision is achieved, auditory or tactile informationis substituted (e.g. Braille, cane travel, etc.). Attempts to remedy oralleviate vision loss have been made by replacing damaged cells or byelectrically stimulating an undamaged proximal level, bypassing impairedcells. Replacement of damaged photoreceptors has been studied in animalsthrough transplantation. Although there are indications thattransplanted photoreceptors can make functional connections, manyquestions remain about the optimal methods to achieve long term graftsurvival and functionality in a human eye.

More recently, visual prostheses have been developed to address theextreme low vision population with retinal degeneration. Electricalstimulation at the primary visual cortex has been attempted and has theadvantage of not requiring a viable optic nerve. However, such corticalstimulation has its own risks, such as exposing the brain to surgicalcomplication and infection.

Stimulation at more distal neuronal locations has received recentattention and may provide an alternative in an outer retinaldegenerative disease such as retinitis pigmentosa. Electricalstimulation of the optic nerve has been used to elicit a sensation ofstreaks or dots (phosphenes). Also, electrical stimulation through acontact lens electrode elicits phosphenes in subjects with advancedphotoreceptor degeneration. These perceptual responses, and theelectrically evoked responses recorded from the scalp in response tosuch stimuli, have been interpreted as evidence that inner retinal cellsin subjects with photoreceptor degeneration retain at least partialfunction. However, the phosphenes elicited with a contact lens electrodeor by electrical stimulation of the optic nerve lack well defined shapeor localization.

The production of a small localized visual percept that might allow thegeneration of a two-dimensional array of phosphenes to provide“pixelized visual input” has been explored in both acute and chronicstudies of blind subjects. Even partial restoration of vision insubjects blind from photoreceptor degeneration has been shown to beimportant.

SUMMARY

According to a first aspect, an external testing device for simulationof a retinal stimulation system implanted on a subject is disclosed, theexternal testing device comprising: a test board unit to simulateelectrical functionalities of the retinal stimulation system; and a testdisplay unit connected to an output of the test board unit, the testdisplay unit visually monitoring the signals processed through the testboard unit, thus simulating a visual effect on the subject of thesignals.

According to a second aspect, a method for externally simulating aretinal stimulation system implanted on a subject is disclosed, themethod comprising: selecting a test board unit to simulate electricalfunctionalities of the retinal stimulation system; and selecting a testdisplay unit for visually monitoring the signals processed through thetest board unit, thus simulating a visual effect on the subject of thesignals.

According to a third aspect, a method for simulating a retinalstimulation system implanted on a subject is disclosed, the methodcomprising: providing a video camera associated with a pair of glasses;capturing an image through the video camera; sending the image to avideo processing unit; converting the image to a digital image;processing the digital image to obtain a processed digital image; andpresenting the processed digital image to a test array system (80)adapted to simulate electrical functionalities of the retinalstimulation system and adapted to visually display signals associatedwith the processed digital image.

Further embodiments are shown in the specification, drawings and claimsof the present application.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows a visual prosthesis apparatus according to the presentdisclosure.

FIGS. 2-3 show a Retinal Stimulation System according to the presentdisclosure.

FIGS. 4-5 show a video capture/transmission apparatus according to thepresent disclosure.

FIG. 6 shows a flexible circuit electrode array according to the presentdisclosure.

FIG. 7 shows components of a fitting system according to the presentdisclosure.

FIG. 8 shows a test array system according to the present disclosure.

FIG. 9 shows an exemplary test array system according to the presentdisclosure.

FIG. 10 shows a Psychophysical Test System (PTS) main screen.

FIG. 11 shows a ‘Simple Direct Stimulation’ computer screen.

FIG. 12 shows an ‘EXPERIMENT: direct stimulation’ message box.

FIG. 13 shows a waveform related to FIG. 12.

FIG. 14 shows a warning dialog box.

FIG. 15 shows an ‘Input Your Comments’ message box.

In the following description, like reference numbers are used toidentify like elements. Furthermore, the drawings are intended toillustrate major features of exemplary embodiments in a diagrammaticmanner. The drawings are not intended to depict every feature of everyimplementation nor relative dimensions of the depicted elements, and arenot drawn to scale.

DETAILED DESCRIPTION

The present disclosure is concerned with an apparatus and a method forindication of visual stimulation. In particular, the present disclosureprovides a method for verifying that a proper visual stimulation isapplied to a visual prosthesis (i.e. device) implanted in an individualpatient (i.e. subject) to create artificial vision.

FIG. 1 shows a visual prosthesis apparatus. The visual apparatusprovides an exemplary implantable Retinal Stimulation System 1 and avideo capture/transmission apparatus embodied in Glasses 5. Theexemplary Retinal Stimulation System 1 is shown in more detail in FIGS.2 and 3 and the exemplary Glasses 5 are shown in more detail in FIGS. 4and 5.

The Retinal Stimulation System 1 is further disclosed in U.S.application Ser. No. 11/207,644, filed Aug. 19, 2005 for “FlexibleCircuit Electrode Array” by Robert J. Greenberg, et, al. incorporatedherein by reference, and is intended for use in subjects with retinitispigmentosa.

The exemplary Retinal Stimulation System 1, shown in FIGS. 2 and 3, isan implantable electronic device containing an inductive coil 116, anelectrode array 2 that is electrically coupled by a cable 3 that piercessclera of the subject's eye to an electronics package 4, external to thesclera. The Retinal Stimulation System 1 is designed, for example, toelicit visual percepts in blind subjects with retinitis pigmentosa.

Human vision provides a field of view that is wider than it is high.This is partially due to fact that we have two eyes, but even a singleeye provides a field of view that is approximately 90° high and 140° to160° degrees wide. It is therefore, advantageous to provide a flexiblecircuit electrode array 2 that is wider than it is tall. This is equallyapplicable to a cortical visual array. In which case, the widerdimension is not horizontal on the visual cortex, but corresponds tohorizontal in the visual scene.

FIG. 6 shows the flexible circuit electrode array 2 prior to folding andattaching to the electronics package 4. A flexible circuit cable 3 isshown in the Figure. At one end of the flexible circuit cable 3 is aninterconnection pad 52 for connection to the electronics package 4. Atthe other end of the flexible circuit cable 3 is the flexible circuitelectrode array 2. Further, an attachment point 54 is provided near theflexible circuit electrode array 2. A retina tack (not shown) is placedthrough the attachment point 54 to hold the flexible circuit electrodearray 2 to the retina. A stress relief 57 may be provided surroundingthe attachment point 54. The stress relief 57 may be made of a softerpolymer than the flexible circuit, or it may include cutouts or thinningof the polymer to reduce the stress transmitted from the retina tack tothe flexible circuit electrode array 2. The flexible circuit cable 3 isformed in a dog leg pattern so than when it is folded at fold 48 iteffectively forms a straight flexible circuit cable 3 with a narrowerportion at the fold 48 for passing through the sclerotomy.

The electronics package 4 of FIGS. 2 and 3 can be electrically coupledto the inductive coil 116. In one aspect, the inductive coil 116 is madefrom wound wire. Alternatively, the inductive coil 116 may be made froma thin film polymer sandwich with wire traces deposited between layersof thin film polymer. The electronics package 4 and the inductive coil116 are held together by a molded body 118 shown in FIG. 3. As alsoshown in FIG. 3, the molded body 118 may also include suture tabs 120shown in FIG. 3. The molded body narrows to form a strap 122 whichsurrounds the sclera and holds the molded body 118, inductive coil 116,and electronics package 4 in place. The molded body 118, suture tabs 120and strap 122 are preferably an integrated unit made of siliconeelastomer. Silicone elastomer can be formed in a pre-curved shape tomatch the curvature of a typical sclera. Furthermore, silicone remainsflexible enough to accommodate implantation and to adapt to variationsin the curvature of an individual sclera. In one aspect, the inductivecoil 116 and molded body 118 are oval shaped, and in this way, a strap122 can better support the oval shaped coil.

The eye moves constantly. The eye moves to scan a scene and also has ajitter motion to prevent image stabilization. Even though such motion isuseless in the blind, it often continues long after a person has losttheir sight. Thus, in one embodiment of the present disclosure, theentire Retinal Stimulation System 1 of the prosthesis is attached to andsupported by the sclera of a subject. By placing the device under therectus muscles with the electronics package in an area of fatty tissuebetween the rectus muscles, eye motion does not cause any flexing whichmight fatigue, and eventually damage, the device.

FIG. 3 shows a side view of the Retinal Stimulation System 1, inparticular, emphasizing the fan tail 124. When the retinal prosthesis isimplanted, the strap 122 is passed under the eye muscles to surround thesclera. The inductive coil 116 and molded body 118 should also followthe strap under the lateral rectus muscle on the side of the sclera. TheRetinal Stimulation System 1 of the visual prosthesis apparatus is verydelicate. It is easy to tear the molded body 118 or break wires in theinductive coil 116. In order to allow the molded body 118 to slidesmoothly under the lateral rectus muscle, the molded body is shaped inthe form of a fan tail 124 on the end opposite the electronics package4. Element 123 shows a retention sleeve, while elements 126 and 128 showholes for surgical positioning and a ramp for surgical positioning,respectively.

Referring to FIGS. 4-5, the Glasses 5 may comprise, for example, a frame11 holding a camera 12, an external coil 14 and a mounting system 16 forthe external coil 14. The mounting system 16 may also enclose the RFcircuitry. In this configuration, the video camera 12 captures livevideo. The video signal is sent to an external Video Processing Unit(VPU) 20 (shown in FIG. 7 and discussed below), which processes thevideo signal and subsequently transforms the processed video signal intoelectrical stimulation patterns or data. The electrical stimulation dataare then sent to the external coil 14 which sends both the data andpower via radio-frequency (RF) telemetry to the coil 116 of the RetinalStimulation System 1. The coil 116 receives the RF commands whichcontrol an application specific integrated circuit (ASIC) which in turndelivers stimulation to the retina of the subject via a thin filmelectrode array (TFEA). In one aspect of an embodiment, light amplitudeis recorded by the camera 12. The VPU 20 may use a logarithmic encodingscheme to convert the incoming light amplitudes into the electricalstimulation patterns or data. These electrical stimulation patterns ordata may then be passed on to the Retinal Stimulation System 1, whichresults in the retinal cells being stimulated via the electrodes in theelectrode array 2. In one exemplary embodiment, the electricalstimulation patterns or data being transmitted by the external coil 14is binary data.

Referring to FIG. 7, a Fitting System (FS) may be used to configure andoptimize the visual prosthesis 3 of the exemplary Retinal StimulationSystem 1. The Fitting System is fully described in the relatedapplication U.S. application Ser. No. 11/796,425, filed on Apr. 27,2007, (Attorney Docket No. S401) which is incorporated herein byreference in its entirety.

The Fitting System may comprise custom software with a graphical userinterface running on a dedicated laptop computer 10. Within the FittingSystem are modules for performing diagnostic checks of the implant,loading and executing video configuration files, viewing electrodevoltage waveforms, and aiding in conducting psychophysical experiments.A video module can be used to download a video configuration file to theVideo Processing Unit (VPU) 20 discussed above and store it innon-volatile memory to control various aspects of video configuration,e.g. the spatial relationship between the video input and theelectrodes. The software can also load a previously used videoconfiguration file from the VPU 20 for adjustment.

The Fitting System can be connected to the Psychophysical Test System(PTS), located for example on a dedicated laptop 30, in order to runpsychophysical experiments. In psychophysics mode, the Fitting Systemenables individual electrode control, permitting clinicians to constructtest stimuli with control over current amplitude, pulse-width, andfrequency of the stimulation. In addition, the psychophysics moduleallows the clinician to record subject responses. The PTS may include acollection of standard psychophysics experiments developed using forexample MATLAB (MathWorks) software and other tools to allow theclinicians to develop customized psychophysics experiment scripts.

The stimulation parameters are checked to ensure that maximum charge perphase limits, charge balance, and power limitations are met before thetest stimuli are sent to the VPU 20 to make certain that stimulation issafe.

Using the psychophysics module, important perceptual parameters such asperceptual threshold, maximum comfort level, and spatial location ofpercepts may be reliably measured. Based on these perceptual parameters,the fitting software enables custom configuration of the transformationbetween video image and spatio-temporal electrode stimulation parametersin an effort to optimize the effectiveness of the retinal prosthesis foreach subject.

The Fitting System laptop 10 of FIG. 7 may be connected to the VPU 20using an optically isolated serial connection adapter 40. Because it isoptically isolated, the serial connection adapter 40 assures that noelectric leakage current can flow from the Fitting System laptop 10.

As shown in FIG. 7, the following components may be used with theFitting System according to the present disclosure. A Video ProcessingUnit (VPU) 20 for the subject being tested, a Charged Battery 25 for VPU20, Glasses 5, a Fitting System (FS) Laptop 10, a Psychophysical TestSystem (PTS) Laptop 30, a PTS CD (not shown), a Communication Adapter(CA) 40, a USB Drive (Security) (not shown), a USB Drive (Transfer) 47,a USB Drive (Video Settings) (not shown), a Patient Input Device (RFTablet) 50, a further Patient Input Device (Jog Dial) 55, Glasses Cable15, CA-VPU Cable 70, CFS-CA Cable 45, CFS-PTS Cable 46, Four (4) PortUSB Hub 47, Mouse 60, Test Array system 80, Archival USB Drive 49, anIsolation Transformer (not shown), adapter cables (not shown), and anExternal Monitor (not shown).

With continued reference to FIG. 7, the external components of theFitting System may be configured as follows. The battery 25 is connectedwith the VPU 20. The PTS Laptop 30 is connected to FS Laptop 10 usingthe CFS-PTS Cable 46. The PTS Laptop 30 and FS Laptop 10 are pluggedinto the Isolation Transformer (not shown) using the Adapter Cables (notshown). The Isolation Transformer is plugged into the wall outlet. Thefour (4) Port USB Hub 47 is connected to the FS laptop 10 at the USBport. The mouse 60 and the two Patient Input Devices 50 and 55 areconnected to four (4) Port USB Hubs 47. The FS laptop 10 is connected tothe Communication Adapter (CA) 40 using the CFS-CA Cable 45. The CA 40is connected to the VPU 20 using the CA-VPU Cable 70. The Glasses 5 areconnected to the VPU 20 using the Glasses Cable 15.

Referring to FIG. 8, the Test Array system 80 according to the presentdisclosure (already briefly discussed with reference to FIG. 7) may beused to verify that a proper visual stimulation is being applied to theRetinal Stimulation System 1 by the external coil 14. The Test Arraysystem 80 may comprise a test board unit 511 and a display unit 512interconnected by cable 513. The person skilled in the art willunderstand that the Test Array system 80 is not limited to having thetest board unit 511 separate from the display unit 512 as shown in FIG.8. In particular, the two units can also be combined into a single unit.

After the Retinal Stimulation System 1 is implanted into the patient itmay be advantageous to externally verify that the data transmitted bythe external coil 14 to the Retinal Stimulation System 1 is correctwithout placing any additional circuitry into the patient. The exemplaryTest Array system 80 may be used to make such verification.

In one exemplary embodiment according to the present application, thetest board unit 511 contains the necessary electronics (ASIC chip,receiving coil etc) to allow simulation of the electrical functionalityof the Retinal Stimulation System 1 described above. To verify that datais being transmitted correctly, the external coil 14 may be placed nearor in contact with the test board unit 511. FIG. 9 shows a test coil 905for transmitting data/power, received from the external coil 14, to theApplication Specific Integrated Circuit (ASIC) 910 of the test boardunit 511. In operation, the ASIC 910 translates the data from theexternal coil 14 into current (pulse) amplitudes that are transmitted tothe LEDs 514 in the display unit 512 through the cable 513. With thehelp of the VPU 20 the external coil 14 may be used to communicate withthe test board unit 511 as if it is communicating with the RetinalStimulation System 1. As far as the external coil 14 is concerned, thetest board unit 511 is the Retinal Stimulation System 1. However,instead of transmitting data to the patient's implant, the signals fromthe external coil 14 may be monitored on the display unit 512. Oneskilled in the art will appreciate that other electronics (switches,amplifiers, etc.) may be incorporated into the test board unit 511 andthe display unit 512 without departing from the spirit and scope of theinvention.

The display unit 512 may contain LEDs 514 or any other types of displays(CRT, video, LCD etc.) to help monitor the signals from the externalcoil 14. In one exemplary embodiment according to the presentapplication, each LED 514 may correspond to a specific electrode in theelectrode array 2. The display unit 512 may also contain a power switch520 to switch on the power supply to the unit 512, a test button 521 toturn on all the LEDs 514 and to test the proper operation of the LEDs514 and their driver circuit.

In one embodiment, the graphical user interface of the Fitting Systemshown in FIG. 7 together with the Test Array system 80 may be used tomake sure that the external coil 14 is able to transmit appropriatesignals to each electrode in the electrode array 2.

In one exemplary embodiment, using Direct Stimulation option in the PTSsystem disclosed above, an experimenter may utilize the Test Arraysystem 80 to (1) design a stimulation wave form for a single or multipleelectrodes and (2) conduct manual testing of the external coil 14.

The Psychophysical Test System (PTS) main screen 139, shown in FIG. 10,has four options: 1) ‘Threshold with method of adjustment’ 140, 2)‘Brightness matching’ 141, 3) ‘Direct Stimulation’ 142, and 4) ‘Quit’143.

A ‘Direct Stimulation’ screen 210 shown in FIG. 11 appears when the‘Direct Stimulation’ button 142 of FIG. 10 is selected from the PTS MainMenu Screen 139 of FIG. 10. The ‘Direct Stimulation’ screen 210 may alsocontain 1) ‘Parameters’ panel 211, 2) ‘Stimulation’ panel 212, 3)‘Message’ panel 213, and 4) ‘Result’ panel 214. During a DirectStimulation experiment, the PTS Server screen on the FS Laptop 10 maydisplay “RUNNING: Direct Stimulation” as shown in FIG. 12.

Configuration parameters may be entered for the experiment as describedbelow with reference to FIG. 11.

Starting stimulation amplitude(s) (μA) for each of the selectedelectrodes may be entered into a ‘Start Amplitude’ window 220 of the‘Parameters’ panel 211. ‘Rastering’ 221 may be used to stagger the starttimes that electrodes are stimulated. When this option is not selected,all electrodes are stimulated simultaneously.

The number of times a stimulation will be repeated may be entered into a‘Repeat Stimulation’ window 222 of the ‘Parameters’ panel 211. The timedelay between successive repetitions may be approximately 0.5 seconds.

The electrodes to be stimulated can be selected from the ‘Electrodes’windows 223 of the ‘Parameters’ panel 211. The electrodes may beindividually selected by clicking individual boxes. Complete rows ofelectrodes may be selected or de-selected by clicking on the alphabeticbutton (A-F). Complete columns of electrodes may be selected orde-selected by clicking on the numeric button (01-10). All electrodescan be selected by using the ‘Set/Clear’ button 224. The inverse of theselected electrodes can be achieved by clicking on the ‘Inverse’ button225.

A Pulse Width (ms) may be entered into windows 226 a-d of the‘Stimulation’ panel 212. A desired time between start of the effectivestimulation window and initiation of the first phase may be entered intoa Tw window 226 a. The duration of the first phase may be entered into aTx window 226 b. The desired time between the end of the first phase andthe beginning of the second phase may be entered into a Ty window 226 c.Duration of the second phase may be entered into a Tz window 226 d. FIG.13 depicts a possible waveform of the numbers entered into windows 226a-d.

The frequency of how many times per second the waveform shown in FIG. 13will be repeated may be entered into a ‘Frequency’ window 228 of the‘Stimulation’ panel 212. A desired length of each stimulation inmilliseconds (i.e. the length of stimulation at a given test amplitude)may be entered into a ‘Duration’ window 229 of the ‘Stimulation’ panel212. Selection of whether the first phase is a negative (cathodic)current phase or a positive (anodic) current phase may be performedusing the first window 227 of the ‘Stimulation’ panel 212. The ‘ShowWaveform’ button 230 may be used to produce a graph that plots thewaveform of the complete stimulus for a trial. The ‘Run’ button 215 maybe used to proceed with the experiment.

After the ‘Run’ button 215 or ‘Show Waveform’ button 230 are activated,the parameters may be checked against safety requirements of the system.If any of the parameters violates safety limits, a message box will bedisplayed and the experimenter will need to change the configurationparameters. Common errors may include broken/shorted electrodes, startamplitudes which exceed a maximum charge per phase limit (or the maximumtotal instantaneous current limit). For example, if there are any brokenelectrodes, the popup message shown in FIG. 14 may be displayed on thescreen. While the experiment is running, the ‘Result’ screen 214 of FIG.11 will indicate that stimulation is in progress. The ‘Cancel’ button216 of FIG. 11 may be used to cancel Stimulation. A message (not shown)may appear indicating that stimulation was stopped by request.

If stimulation has ended normally, a Comment screen 236 shown in FIG. 15may be displayed. The Comment screen 236 contains two buttons, ‘RepeatLast Experiment’ 237 and ‘Go Back to Main Menu’ 238. If Repeat LastExperiment 237 is chosen, the experimenter will be returned to the mainDirect Stimulation screen 210 with the Parameters from the lastexperiment and the experimenter can modify and repeat the experiment. If‘Go Back to Main Menu’ 238, is chosen, the experimenter will be returnedto the main PTS menu 139.

In one exemplary embodiment, by selecting all the electrodes with thebutton 224; by selecting “Rastering” 221; by selecting the “StartAmplitude” 220 to be 10 μA; by selecting the Tx 226 b, Ty 226 c, Tz 226d and Tw 226 a to be 0.45 ms; by choosing Frequency 228 to be 60 Hz; andby choosing Duration 229 to be 250 ms it is possible to make sure thatthe external coil 14 transmits data to all the electrodes in theelectrode array 2 if all the LED 514 are lit continuously for theduration of the stimulus.

In another embodiment, by selecting all the electrodes with the button224; by selecting “Rastering” 221; by selecting the “Start Amplitude”220 to be 30 μA; by selecting the Tx 226 b, Ty 226 c, Tz 226 d and Tw226 a to be 0.45 ms; by choosing Frequency 228 to be 60 Hz; and bychoosing Duration 229 to be 250 ms it is possible to make sure that theexternal coil 14 transmits data at higher power to all the electrodes inthe electrode array 2 if all the LED 514 are lit continuously andbrighter compared to the above embodiment.

In one exemplary embodiment, the Test Array system 80 may bereconfigurable so as to be able to verify that a proper visualstimulation is being applied to an implant other than the RetinalStimulation System 1. The Test Array system 80 may be reconfiguredeither using the graphical user interface of the Fitting System shown inFIG. 7 or through a hard-wired switch (not shown).

The following concepts are supported by the present application:

Concept 1. An external testing device for simulation of a retinalstimulation system implanted on a subject, comprising:

a test board unit to simulate electrical functionalities of the retinalstimulation system; and

a test display unit connected to an output of the test board unit, thetest display unit visually monitoring the signals processed through thetest board unit, thus simulating a visual effect on the subject of thesignals.

Concept 2. The external testing device of Concept 1, wherein the testboard unit and the test display unit are two separate components.

Concept 3. The external testing device of Concept 1, wherein the testboard unit and the test display unit are part of a single component.

Concept 4. The external testing device of Concept 1, further comprisingan external coil connectable with the test board unit and adapted tosend signals to the test board unit.

Concept 5. The external testing device of Concept 4, wherein theexternal coil is configured to receive stimulation patterns from a videoprocessing unit, wherein the stimulation patterns are based on visualsignals processed by the video processing unit.

Concept 6. The external testing device of Concept 1, wherein the testdisplay unit comprises a plurality of visualization devices.

Concept 7. The external testing device of Concept 6, wherein eachvisualization device of the plurality of visualization devicescorresponds to a specific electrode of an array of electrodes of theretinal stimulation system.

Concept 8. The external testing device of Concept 1, wherein the testdisplay unit comprises a power switch to switch on power supply to thetest display unit.

Concept 9. The external testing device of Concept 6, wherein the testdisplay unit comprises a test button to turn on all visualizationdevices of the plurality of visualization devices.

Concept 10. The external testing device of Concept 1, wherein the testboard unit is configured to process logarithmic electrical signals.

Concept 11. The external testing device of Concept 4, wherein theexternal coil is adapted to send logarithmic electrical signals to thetest board unit.

Concept 12. The external testing device of Concept 10, wherein the testboard unit is configured to process the logarithmic electrical signals.

Concept 13. The external testing device of Concept 1, wherein the testboard unit is adapted to simulate electrical functionalities of anotherretinal stimulation system, wherein the signals to the retinalstimulation system do not correspond to the signals to the anotherretinal stimulation system.

Concept 14. A method for externally simulating a retinal stimulationsystem implanted on a subject, the method comprising:

providing a test board unit to simulate electrical functionalities ofthe retinal stimulation system; and

providing a test display unit for visually monitoring the signalsprocessed through the test board unit, thus simulating a visual effecton the subject of the signals.

Concept 15. The method of Concept 14, wherein the test board unit andthe test display unit are two separate components.

Concept 16. The method of Concept 14, wherein the test board unit andthe test display unit are part of a single component.

Concept 17. The method of Concept 14, wherein the signals processedthrough the test board unit are from an external coil.

Concept 18. The method of Concept 17, further comprising selecting avideo processing unit adapted to process visual signals and transformthe visual signals to stimulation patterns to be sent to the externalcoil.

Concept 19. The method of Concept 14, wherein the test display unitcomprises a plurality of visualization devices.

Concept 20. The method of Concept 19, wherein each visualization deviceof the plurality of visualization devices corresponds to a specificelectrode of an array of electrodes of the retinal stimulation system.

Concept 21. The method of Concept 14, wherein the test display unitcomprises a power switch to switch on power supply to the test displayunit.

Concept 22. The method of Concept 19, wherein the test display unitcomprises a test button to turn on all visualization devices of theplurality of visualization devices.

Concept 23. The method of Concept 14, wherein the test board unit isconfigured to process logarithmic electrical signals.

Concept 24. The method of Concept 17, wherein the signals from theexternal coil are logarithmic electrical signals.

Concept 25. The external testing device of Concept 23, wherein the testboard unit is configured to process the logarithmic electrical signals.

Concept 26. The method of Concept 14, wherein the test board unit isadapted to simulate electrical functionalities of another retinalstimulation system, wherein the signals to the retinal stimulationsystem do not correspond to the signals to the another retinalstimulation system.

Concept 27. A method for simulating a retinal stimulation systemimplanted on a subject, the method comprising:

providing a video camera associated with a pair of glasses;

capturing an image through the video camera;

sending the image to a video processing unit;

converting the image to a digital image;

processing the digital image to obtain a processed digital image; and

presenting the processed digital image to a test array system adapted tosimulate electrical functionalities of the retinal stimulation systemand adapted to visually display signals associated with the processeddigital image.

Concept 28. The method of Concept 27, wherein the test array systemcomprises:

a test board unit for processing the signals associated with theprocessed digital image; and

a test display unit for visually monitoring the signals processedthrough the test board unit.

Accordingly, what has been shown is an improved method of verifying thata proper visual stimulation is being applied to the implant device.While the invention has been described by means of specific embodimentsand applications thereof, it is understood that numerous modificationsand variations could be made thereto by those skilled in the art withoutdeparting from the spirit and scope of the invention. It is therefore tobe understood that within the scope of the claims, the invention may bepracticed otherwise than as specifically described herein.

1. A method for externally simulating a retinal stimulation system implanted on a subject, the method comprising: providing a test board unit to simulate electrical functionalities of the retinal stimulation system; and providing a test display unit for visually monitoring the signals processed through the test board unit, thus simulating a visual effect on the subject of the signals.
 2. The method of claim 1, wherein the test board unit and the test display unit are two separate components.
 3. The method of claim 1, wherein the test board unit and the test display unit are part of a single component.
 4. The method of claim 1, wherein the signals processed through the test board unit are from an external coil.
 5. The method of claim 1, further comprising selecting a video processing unit adapted to process visual signals and transform the visual signals to stimulation patterns to be sent to the external coil.
 6. The method of claim 1, wherein the test display unit comprises a plurality of visualization devices.
 7. The method of claim 6, wherein each visualization device of the plurality of visualization devices corresponds to a specific electrode of an array of electrodes of the retinal stimulation system.
 8. The method of claim 1, wherein the test display unit comprises a power switch to switch on power supply to the test display unit and a test button to turn on all visualization devices of the plurality of visualization devices.
 9. The method of claim 1, wherein the test board unit is adapted to simulate electrical functionalities of another retinal stimulation system, wherein the signals to the retinal stimulation system do not correspond to the signals to the another retinal stimulation system.
 10. A method for simulating a retinal stimulation system implanted on a subject, the method comprising: providing a video camera associated with a pair of glasses; capturing an image through the video camera; sending the image to a video processing unit; converting the image to a digital image; processing the digital image to obtain a processed digital image; and presenting the processed digital image to a test array system adapted to simulate electrical functionalities of the retinal stimulation system and adapted to visually display signals associated with the processed digital image.
 11. The method of claim 10, wherein the test array system comprises: a test board unit for processing the signals associated with the processed digital image; and a test display unit for visually monitoring the signals processed through the test board unit. 